No cycle lanes on pavements are for the exclusive use of cyclists.
This is technically true (by virtue of the fact that pedestrians seem generally permitted to be pretty much anywhere, to use roads which don't have a footway (of course), except for when the “no pedestrians” sign is present, or implied by other context, e.g. motorway signs) but it's certainly not a good idea to encourage pedestrians to walk in cycleways, since it renders them essentially completely pointless. We may not have jaywalking laws in the UK, but we do have a measure of common sense required, and once it becomes the norm to walk in cycleways, … the cyclists are back out on the road and the infrastructure work was pointless, since the cycleway is essentially unusable …
At the link
https://www.gov.uk/guidance/the-highway-code/traffic-signs , search forward for “segregated”, and you'll find the sign which indicates a “segregated” path for cycles and (on the other side of the white line) pedestrians. On such paths it's certainly extremely bad form, somewhere between impolite and dangerous, though not illegal, for a pedestrian to be on the cycle side. They're allowed to There's another “shared” sign, oddly not present on that page, which indicates a shared and unsegregated path in which the whole area is available to both cyclists and pedestrians (no separating line) and common sense and courtesy have to prevail.
Rule 62 at
https://www.gov.uk/guidance/the-highway-code/rules-for-cyclists-59-to-82 states “Cycle Tracks. These are normally located away from the road, but may occasionally be found alongside footpaths or pavements. Cyclists and pedestrians may be segregated or they may share the same space (unsegregated). When using segregated tracks you MUST keep to the side intended for cyclists as the pedestrian side remains a pavement or footpath.”
— and there's the asymmetry! Cyclists /must/ keep to the cycle side, but pedestrians may stray with impunity.
Rule 13 at
https://www.gov.uk/guidance/the-highway-code/rules-for-pedestrians-1-to-35 states “Some cycle tracks run alongside footpaths or pavements, using a segregating feature to separate cyclists from people on foot. Segregated routes may also incorporate short lengths of tactile paving to help visually impaired people stay on the correct side. On the pedestrian side this will comprise a series of flat-topped bars running across the direction of travel (ladder pattern). On the cyclist side the same bars are orientated in the direction of travel (tramline pattern). Not all routes which are shared with cyclists are segregated. Take extra care where this is so (see Rule 62).”
Clearly none of this explicitly states that it is not
legal for pedestrians to walk on the “cyclist side” but tacitly indicates that it is important for both to stay on the “correct side”. Clearly a cyclist on the “wrong side” is breaking the law, but a pedestrian on the “wrong side” probably isn't, from my reading so far. It's just stupid, annoying, and dangerous, and renders the cycle path worse than useless.
In the end, that's why most experienced cyclists simply avoid such paths — they're too frustrating (and frequently dangerous) to use, compared to using the main carriageway.
More discussion at
http://www.cyclinguk.org/article/campaign-article/new-guidance-on-shared-use-routes — and a detailed overview at
http://www.bikehub.co.uk/featured-articles/cycling-and-the-law/
No idea what I'm supposed to do regarding the linking / quotation rules here: if I were to copy and paste swathes from the above links then I'd be infringing their copyright … but to fail to provide the links would be to reduce greatly the amount of information I'm trying to get across. There's always the wayback machine, once the original sites disappear, and so I'll ensure they're archived there for future reference in case the originals disappear.